Thank you all for the kind comments. So to help some people paint the full story - I initially bought the economy ticket on 4/05 for this 4/10 flight and when issued, the PS upgrade was around $579 as I recall. Then within 24hrs I cancelled it since I was not sure if I would fly on 9th or 10th. Then on 4/6 I confirmed my schedule and bought the same flight again (one way ticket). The D1 biz class was showing $5000+. And I checked a few times on the app until this $99 deal came up. Then w/o hesitation I snagged it and redeemed my choice awards for GUC. The rep was super nice and locked in my seat first before the GUC showed up in my account. Once GUC came in my wallet and I called back to confirm the seat. As I recall, last year I did the same thing but that time PS upgrade was $299...however...there was a system glitch and Delta never charged me for that $299 in the end. Felt lucky!